I just want to underscore Elliott's point about how hard polling has gotten with a quick story I wrote up in a paper with Tori Gorton called "On the Internet, No One Knows You're An Activist." We were trying to survey lower-engagement voters, so we drew a sample of 9,937 registered Pennsylvania voters who hadn't consistently voted 2012-2018. Then, we matched them to Facebook accounts and served ads to 1,321 inviting them to take a survey. 66 people clicked on our ad, 7 began the survey, 6 completed it, and 1 person left an email for follow-up. I of course want to express my deep gratitude to that one respondent. But beyond that, a 0.4% response rate magnifies sampling errors, because very small differences in people's willingness to take polls can add up to very large errors in vote margins. That's especially true in primaries, where pollsters can't use partisan identification to stabilize the results.

—Dan Hopkins, 538 contributor

We've been tracking Trump's non-incumbent endorsees (because endorsing the incumbent is kind of a gimme) tonight, and so far he's 4 for 4 of the races called. Addison McDowell, Trump's pick in North Carolina's GOP primary for the 6th District, is also leading. But in California, state Assemblyman Vince Fong, who received Trump's endorsement for the Republican primary in the state's 20th District (Kevin McCarthy's old seat), is trailing at 26 percent with 23 percent of the expected vote reporting.

—Kaleigh Rogers, 538

It has become somewhat of a theme of our live blogs this primary calendar to note that Trump's challengers are beating their polls. This first looked to be the case in New Hampshire, where polls significantly underestimate support among Republican likely voters for Haley. But the pattern is more robust than one state: In fact Haley has been beating her polls by an average of five points (in vote share) once you account for undecided voters in these surveys. The consistency of this pattern is striking enough to warrant a post on the matter.

As Mary said earlier, polling primaries is hard! That is betrayed by the fact that POTUS primary polls are by far the least accurate type of poll in 538's pollster rating database going back to 1999. But error is different than bias, and when most of the polls are off in the same direction, something has gone awry.

That "something" is likely the difficulty in obtaining opinions of moderate Republicans from samples of "likely Republican primary voters." Remember that fewer than one percent of people called for a poll actually complete the interview. That means the ones that do are statistical "weirdos" (excuse the technical language). Pollsters adjust for this by weighting their samples to known population benchmarks — like the percent of all adults who are white, over 65, have a college education etc. But in primaries, such benchmarks do not actually exist; pollsters are just making educated guesses about them.

My theory is that most of these primary polls pulling samples of voters from voter registration lists are missing moderate crossover partisans and first-time voters. Additionally, we know that people who are highly motivated to participate in polls (the "weirdos") also happen to be the most politically and ideologically extreme Americans. That's a recipe for polling bias in primaries, where weighting to party, past vote and polarized demographic benchmarks does not control for the partisan consequences of overrepresenting politically engaged Americans.

Now, none of this is to say that polling is "broken." It's just hard to precisely sample a population that doesn't really exist. The polls for the 2024 primary still have below-average error, historically speaking, so we shouldn't go throwing out the baby with the bathwater. But this could nevertheless be a sign of pollsters having a hard time reaching moderate "normie" voters. And if that persists, it could have consequences for general election polls too.

—G. Elliott Morris, 538

In California's 40th District, with 46 percent of the expected vote in according to the Associated Press, engineer Allyson Damikolas (endorsed by EMILY's List), is trailing former fire captain Joe Kerr (endorsed by the Congressional Progressive Caucus PAC). The 40th is a key target for Democrats, who are looking to win back some of the ground they gained (and then lost) in the Orange County area. The 40th District spans Riverside and San Bernardino Counties, too.

—Meredith Conroy, 538 contributor

The race for Senate in Texas will surely be one of the most closely watched races of the year. There are nine candidates running in the Democratic primary to unseat Sen. Ted Cruz, but the front-runner is Rep. Colin Allred, a former NFL player and civil rights attorney who has represented the Dallas area since 2019. Allred has raised the most funds (to the tune of $21 million) and attracted donations from party influencers. The biggest question tonight is whether Allred can pull more than 50 percent of the vote and avoid a May runoff.

There are also a handful of U.S. representatives in Texas with at least some danger of losing their seats tonight, as Jacob covered earlier. Keep your eyes on Houston Democrat Lizzie Fletcher in the 7th District, who is facing a challenger from the left in Pervez Agwan; Democrat Sheila Jackson Lee in the 18th District, whose run for Houston mayor last year destabilized her campaign against former Houston City Councilwoman Amanda Edwards; and Republican Tony Gonzales in the 23rd District, who is facing multiple challengers and may also end up in runoff territory.

And there are some open seats up for grabs, creating hotly contested primary races. In the 12th District around Fort Worth, it's the familiar GOP battle between results-focused conservatism of the old guard versus the firebrand populism of MAGA. State Rep. Craig Goldman represents the establishment candidate, while business owner John O'Shea fills the role of MAGA candidate. In the 26th District, two far-right candidates are leading a slate of 11 to fill the open seat in this deep-red stronghold: Brandon Gill, who heavily promoted his father-in-law, Dinesh D'Souza's, conspiracy-theory-laden film "2000 Mules" on his website, and Southlake Mayor John Huffman. And lastly, with Allred making a play for the Senate, his Dallas-area 32nd District is up for grabs. Ten Democrats are running in the primary, though two in particular seem to be leading the pack: state Rep. Julie Johnson and trauma surgeon Brian Williams.

If you're interested in reading more on these races, check out my full preview from last week. Otherwise, I'll have more on these races and other takeaways from Texas after polls begin to close there at 8 p.m. Eastern.

—Kaleigh Rogers, 538